I agree with Woofie, I think you want to get 1/8 teaspoon into each 4" pot.
((Edited to correct earlier mistake - thank you, Woofie!))
>> ("sufficient water to wet the potting soil thoroughly")
I guessed that they want to expose all of the soil but not waste mush dripping out the bottom. (Like a "drench" but not wasteful.) But it is a systemic insecticide, so that shouldn't be crucial.